Mine just came in a couple of hours back. Pretty impressed so far. Very small, nice solid build. Through my MS1i's the sound is definitely more controlled and refined, not so 'peaky' and 'grating' in the top end.
With the Phonaks the detail really lets loose. Bass is tight and the midrange is very nice: a little forward IMO but sweet, a little warm and without sibilance.
A quick A/B with the iPhone, I thought the iPhones HP out sounded 'softer around the edges' while the uDac sounded 'sharper' without being aggressive. Nice!